CN112800786A

CN112800786A - Passive tag and starting method thereof

Info

Publication number: CN112800786A
Application number: CN201911107568.2A
Authority: CN
Inventors: 易俊; 刘健
Original assignee: Zhejiang Johar Technology Co ltd
Current assignee: Zhejiang Johar Technology Co ltd
Priority date: 2019-11-13
Filing date: 2019-11-13
Publication date: 2021-05-14

Abstract

A passive tag and a method for activating the same, the passive tag comprising: the processing module is used for receiving a command signal sent by the reader; the energy collecting module is coupled with the processing module and used for collecting and storing the energy transmitted by the reader and supplying power to the processing module during the operation of the processing module. The scheme provided by the invention can effectively prolong the working distance of the passive tag, has low cost, small volume and high safety, does not need to add extra hardware on the corresponding reader side, and is beneficial to implementation.

Description

Passive tag and starting method thereof

Technical Field

The invention relates to the technical field of passive tags, in particular to a passive tag and a starting method thereof.

Background

The energy and command of a common Radio Frequency Identification (RFID) tag are simultaneously transmitted from a reader to the tag, i.e., a Power Path (Power Path) and a Communication link (Communication link) are simultaneously, and simultaneously. The power path typically requires much more power consumption than the communication link, and therefore, the power path becomes a major factor limiting the operating distance of the tag. Therefore, the instantaneous operating power of the tag must be approximately equal to the instantaneous power received by the antenna. Various methods have been used to increase the working distance.

For example, active tags provide a source of energy through a battery, and the limitation on their operating distance comes primarily from the communication link. Thus, the working distance of active tags is typically much longer than that of passive tags. However, the cost, size, and safety of adding batteries to the tag may become unacceptable in some applications.

For another example, other energy harvesting methods, such as solar energy, have been attempted to provide operating energy to the tag. Although the mode cancels the battery and eliminates the potential safety hazard, the solar panel greatly increases the cost and the volume.

For another example, tags having different frequencies for the power path and the communication link have been adopted, with the power path operating at 433MHz and the communication link operating at 908 MHz. This dual frequency mode can extend the operating distance but requires two antennas. In contrast, the additional cost in terms of tags seems to be low, since only one antenna needs to be added. However, on the reader side, a custom reader is required to operate in both frequency bands, which may be more expensive.

In summary, the prior art cannot provide a suitable passive tag, which can take into account working distance, cost, size and safety.

Disclosure of Invention

The invention aims to provide an improved passive tag and a starting method thereof, which can take working distance, cost, volume and safety into consideration.

To solve the above technical problem, an embodiment of the present invention provides a passive tag, including: the processing module is used for receiving a command signal sent by the reader; the energy collecting module is coupled with the processing module and used for collecting and storing the energy transmitted by the reader and supplying power to the processing module during the operation of the processing module.

Optionally, the supplying power to the processing module during the operation of the processing module includes: when the energy collected by the energy collection module reaches a preset threshold value and/or a trigger instruction sent by the reader is received, the energy collection module starts to supply power to the processing module.

Optionally, the preset threshold is determined according to energy consumed by a single operation of the passive tag.

Optionally, the energy collection module includes: the energy conversion module is used for converting the radio frequency energy transmitted by the reader into direct current energy; the energy storage module is coupled with the energy conversion module and used for storing the energy converted by the energy conversion module; a trigger switch switchable between an open state and a closed state to break or make an electrical connection between the energy storage module and the processing module.

Optionally, the energy collection module further comprises: and the voltage detection module is coupled with the energy storage module and used for detecting whether the energy stored by the energy storage module reaches a preset threshold value or not, and the voltage detection module is also coupled with the trigger switch and used for controlling the trigger switch to be switched to a closed state when detecting that the energy stored by the energy storage module reaches the preset threshold value.

Optionally, the energy collection module further comprises: and the handshake module is used for receiving a trigger instruction sent by the reader, is coupled with the trigger switch, and controls the trigger switch to be switched to a closed state when receiving the trigger instruction.

Optionally, the energy collection module further comprises: the voltage detection module is coupled with the energy storage module and used for detecting whether the energy stored by the energy storage module reaches a preset threshold value; the handshake module is used for receiving a trigger instruction sent by the reader; and the AND gate is coupled with the voltage detection module, the handshake module and the trigger switch, and controls the trigger switch to be switched to a closed state when a first message received from the voltage detection module indicates that the energy stored by the energy storage module reaches the preset threshold value and a second message received from the handshake module indicates that the trigger instruction is received.

Optionally, the handshake module includes: the handshake signal processing submodule is used for identifying handshake signals from the signals sent by the reader; and the counter is coupled with the handshake signal processing submodule to calculate the number of the received handshake signals, and when the number of the received handshake signals reaches a preset number, the trigger instruction is determined to be received.

Optionally, the length of the low level of the handshake signal is different from the length of the low level of the command signal, or the length of the high level of the handshake signal is different from the length of the high level of the command signal.

Optionally, the handshake signal processing sub-module includes: the voltage regulator comprises a first resistor, a second resistor, a third resistor, a fourth resistor and a first switch, wherein a first end of the first resistor and a first end of the first switch are connected to a voltage source in parallel, a second end of the first switch and a first end of the third resistor are connected in series, a second end of the first resistor and a first end of the second resistor are connected in series, a second end of the third resistor and a first end of the fourth resistor are connected in series, a second end of the second resistor is grounded, and a second end of the fourth resistor is grounded; the first demodulator is used for demodulating a signal sent by the reader, the signal is a handshake signal or a command signal, and the first demodulator controls the first switch to be opened or closed according to the high-low level of the demodulated signal; a first capacitor connected in parallel with the fourth resistor; the comparator is used for comparing the difference between a first voltage and a second voltage, the first voltage is the voltage value of the second end of the first resistor, the second voltage is the voltage value of the first capacitor, when the signal sent by the reader is a command signal, the comparator outputs a first comparison result, when the signal sent by the reader is a handshake signal, the comparator outputs a second comparison result, and the second comparison result is used for indicating and identifying the handshake signal.

Optionally, when the signal demodulated by the first demodulator is at a high level, the first switch is controlled to be closed, and when the signal demodulated by the first demodulator is at a low level, the first switch is controlled to be opened.

Optionally, a low level length of the handshake signal is greater than a low level length of the command signal, the first comparison result includes only a high level signal or a low level signal, and the second comparison result includes a high level signal and a low level signal.

In order to solve the above technical problem, an embodiment of the present invention further provides a method for starting a passive tag, where the passive tag includes the passive tag, and the starting method includes: receiving a first sequence; performing an energy harvesting operation according to the first sequence; after the energy harvesting operation is completed, receiving a second sequence, the second sequence including the command signal.

Optionally, the first sequence includes: a charging sequence comprising a plurality of consecutive high levels; an indication sequence is initiated, including at least one handshake signal.

Optionally, the length of the charging sequence is determined according to a distance from the reader.

Optionally, after the energy harvesting operation is completed and before the second sequence is received, the starting method further includes: receiving a trigger instruction; receiving the second sequence in response to receiving the trigger instruction.

Compared with the prior art, the technical scheme of the embodiment of the invention has the following beneficial effects:

an embodiment of the present invention provides a passive tag, including: the processing module is used for receiving a command signal sent by the reader; the energy collecting module is coupled with the processing module and used for collecting and storing the energy transmitted by the reader and supplying power to the processing module during the operation of the processing module.

Compared with the real-time power supply design adopted by the existing passive tag, the passive tag is additionally provided with a charging process at the beginning of starting, the newly added energy collection module is used for fully collecting the radio frequency energy of the reader, and the processing module is powered by the energy collection module during the subsequent normal starting and working periods, so that the limitation of the processing module on the working distance is basically eliminated. Specifically, because the power consumption of the energy collection module is significantly less than that of the processing module, according to the energy transmission principle that the distance and the energy are in an inverse square relationship, on the premise that the radio frequency energy of the reader is not changed, because the load is reduced, the energy required by charging the passive tag in this embodiment is reduced, even if the distance from the passive tag to the reader is increased, the passive tag in this embodiment can still effectively complete the charging operation, so that the extension of the working distance becomes possible. Further, in the radio frequency same-frequency energy collection tag provided by this embodiment, the power path and the communication link are still the same-frequency and the same-source, and the radio frequency energy of the reader is collected in the special energy collection module first, and after the charging is completed, the passive tag of this embodiment starts to perform normal command transceiving operation. From the hardware aspect, the passive tag can be realized only by additionally arranging an energy collecting module in the passive tag, and great advantages are achieved in cost, volume and safety. For the reader, additional hardware is not needed, and the implementation is facilitated.

The embodiment of the invention also provides a method for starting the passive tag, wherein the passive tag comprises the passive tag, and the starting method comprises the following steps: receiving a first sequence; performing an energy harvesting operation according to the first sequence; after the energy harvesting operation is completed, receiving a second sequence, the second sequence including the command signal.

Compared with the technical scheme that the starting and charging of the conventional passive tag are completed based on the same sequence, the starting operation and the charging operation in the starting method are asynchronously realized, when the second sequence is received, the energy supporting the working of the processing module is mainly derived from the energy collection module rather than the radio frequency energy of the reader, and because the power consumption of the energy collection module is significantly smaller than that of the processing module, even if the distance between the passive tag and the reader in the embodiment is further increased compared with the limit working distance of the conventional passive tag, so that the energy is greatly lost when the first sequence and the second sequence reach the passive tag in the embodiment, the passive tag in the embodiment can still effectively charge based on the first sequence and complete normal command transceiving operation based on the second sequence, so that the working distance can be prolonged.

Drawings

FIG. 1 is a logic block diagram of a passive tag of the prior art;

FIG. 2 is a timing diagram of a start-up process of the passive tag of FIG. 1;

FIG. 3 is a logic block diagram of a passive tag of an embodiment of the present invention;

FIG. 4 is a sequence diagram of a command signal of the prior art;

FIG. 5 is a sequence diagram of a handshake signal according to an embodiment of the present invention;

FIG. 6 is a logic block diagram of a handshake signal processing submodule according to an embodiment of the present invention;

FIG. 7 is a diagram illustrating the recognition results of the command signals of FIG. 4 using the handshake signal processing sub-module of FIG. 6;

FIG. 8 is a diagram illustrating the recognition results of the command signals of FIG. 5 using the handshake signal processing sub-module of FIG. 6;

FIG. 9 is a flow chart of a method for activating a passive tag according to an embodiment of the present invention;

FIG. 10 is a timing diagram of a start-up process of the passive tag of FIG. 3 using the start-up method of FIG. 9;

FIG. 11 is a graph of minimum required received power versus RF energy harvesting time for the passive tag of FIG. 1 and the passive tag of FIG. 3 at a first chip power consumption;

fig. 12 is a graph of minimum required received power versus rf energy harvesting time for the passive tag of fig. 1 and the passive tag of fig. 3 for a second chip power consumption.

Detailed Description

As background, existing passive tags fail to provide both working distance and cost, volume, and security.

Specifically, referring to fig. 1, the existing passive tag 1 may include: a receiving antenna 10 (also called a tag antenna), a Rectifier (Rectifier)11, a Demodulator (Demodulator)12, a Modulator (Modulator)13, a Low Dropout Regulator (LDO) 14, other modules 15, and an on-chip capacitor 16. Among others, the other modules 15 may include: a Power On Reset (POR) unit, a Clock (CLK) unit, a baseband (BB) unit, and the like.

Further, the demodulator 12, the modulator 13, the LDO14, the other module 15, and the on-chip capacitor 16 may be collectively referred to as a processing module, which is used as a load of the rectifier 11, and radio frequency energy of a reader (not shown) received from the receiving antenna 10 is converted into direct current energy by the rectifier 11, and then stored in the on-chip capacitor 16, and further provided to each load.

Referring to fig. 2, the reader transmits an R ═ T sequence, and within the power-up time (T _ power-up), the finisher 11 charges the on-chip capacitor 16, and VC and VDD both rise. When VDD reaches the power-on reset POR threshold, a POR pulse is generated, so far, the BB unit is ready to operate to receive commands.

Existing protocols provide for short power-up times, such as 2.5 milliseconds (ms), after which the R ═ T sequence also includes delimiters (delimiters), command signals (data-0), and forward link calibration symbols (RTcal).

During the command signal, the high level represents that the reader sends a continuous wave, the corresponding passive tag 1 receives a command during the period, and meanwhile, the rectifier 11 charges the on-chip capacitor 16; a low level represents a decay state during which the passive tag 1 is maintained in operation by the on-chip capacitor 16.

This results in the voltage of the on-chip capacitor 16 being repeatedly ramped down during the command signal and the rectifier 11, each time charging the on-chip capacitor 16, pre-retaining the energy that would have been consumed before the second charge in addition to complementing the energy that had been consumed after the previous charge.

The inventor of the present application has found through analysis that, based on the device structure and the operation mode of the passive tag 1 shown in fig. 1 and fig. 2, the rf energy of the reader is directly hooked to all loads of the rectifier 11, and the rectifier 11 converts the rf energy of the reader into dc energy in real time for the loads to use, both during the start-up phase and during the operation, and since the loads such as the demodulator 12, the modulator 13, the LDO14, and the other modules 15 have large power consumption, in combination with the energy transmission principle that the distance and the energy are inversely related, the distance between the reader and the passive tag 1 is strictly limited in order to ensure that the on-chip capacitor 16 can store enough power to support the operation of each load.

Compared with the real-time power supply design adopted by the existing passive tag, the passive tag is additionally provided with a charging process at the beginning of starting, the newly added energy collection module is used for fully collecting the radio frequency energy of the reader, and the processing module is powered by the energy collection module during the subsequent normal starting and working periods, so that the limitation of the processing module on the working distance is basically eliminated.

Specifically, because the power consumption of the energy collection module is significantly less than that of the processing module, according to the energy transmission principle that the distance and the energy are in an inverse square relationship, on the premise that the radio frequency energy of the reader is not changed, because the load is reduced, the energy required by charging the passive tag in this embodiment is reduced, even if the distance from the passive tag to the reader is increased, the passive tag in this embodiment can still effectively complete the charging operation, so that the extension of the working distance becomes possible.

Further, in the radio frequency same-frequency energy collection tag provided by this embodiment, the power path and the communication link are still the same-frequency and the same-source, and the radio frequency energy of the reader is collected in the special energy collection module first, and after the charging is completed, the passive tag of this embodiment starts to perform normal command transceiving operation. From the hardware aspect, the passive tag can be realized only by additionally arranging an energy collecting module in the passive tag, and great advantages are achieved in cost, volume and safety. For the reader, additional hardware is not needed, and the implementation is facilitated.

In other words, the passive tag according to this embodiment first charges the energy collection module based on the radio frequency energy of the reader, and then the energy collection module supplies power to the processing module during actual operation. Therefore, during the working period of the passive tag, the radio frequency energy of the reader basically only needs to meet the power consumption of the demodulator and the energy collecting module, the power consumption of the demodulator and the energy collecting module is obviously smaller than that of other devices in the processing module, most devices in the processing module do not depend on the real-time energy of the reader any more, the limitation of the processing module on the working distance is eliminated, and the working distance is effectively prolonged.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.

Fig. 3 is a logic block diagram of a passive tag of an embodiment of the present invention. The passive tag can be applied to the scene of collecting the same-frequency energy of the ultrahigh frequency RFID.

Specifically, referring to fig. 3, the passive tag 2 according to this embodiment may include: a processing module 20, configured to receive a command signal sent by a reader (not shown); an energy collecting module 21 coupled to the processing module 20 for collecting and storing energy transmitted by the reader and supplying power to the processing module 20 during operation of the processing module 20.

In one implementation, the passive tag 2 may further include a receiving antenna 22 (also referred to as a tag antenna) for receiving the rf energy and command signals of the reader, wherein the rf energy and command signals may be integrally transmitted and received in a sequence, and the sequence may be an rf signal. Further, the passive tag 2 may also transmit tag information to the reader through the antenna 22.

In one implementation, the processing module 20 may be understood as a core (core) of the passive tag 2 for processing the sequence received by the antenna 22 and responding.

In one implementation, the processing module 20 may include: a second demodulator 200, a modulator 201, an LDO202, other modules 203, and an on-chip capacitor 204. Among others, the other modules 203 may include: POR) cells, CLK cells, BB cells, etc.

In particular, the second demodulator 200 may be coupled to the antenna 22 to convert attenuated/non-attenuated changes of the radio frequency signals received by the antenna 22 into high/low level changes.

In one implementation, the on-chip capacitor 204 is coupled to the energy harvesting module 21, and during operation, the energy harvesting module 21 supplies power to the on-chip capacitor 204 to maintain the operation of other devices in the processing module 20 through the on-chip capacitor 204.

Specifically, the operating period refers to the period of time during which the command signal sent by the reader is received and responded. To ensure accurate receipt of the command signal, the active period may also be covered forward for a period of time, such as including a normal start-up procedure prior to receipt of the command signal. For example, the period from the power-on time to the RTcal in fig. 2 may be regarded as the operation period. The difference with the passive tag 1 shown in fig. 1 and 2 is that in the present embodiment, the passive tag 2 is powered by its own energy harvesting module 21 during this period of operation.

In one implementation, the second demodulator 200 and the modulator 201 are respectively coupled to the antenna 22 to receive the sequence transmitted by the reader.

In one implementation, the modulator 201, LDO202, and other modules 203 are coupled to the on-chip capacitance 204. In other words, during operation, in the processing module 20, only the second demodulator 200 directly maintains operation through the rf energy of the reader, the operation energy of each other module is derived from the on-chip capacitor 204, and the energy of the on-chip capacitor 204 is derived from the pre-charged energy collection module 21.

In one implementation, the energy harvesting module 21 may include: an energy conversion module 210, configured to convert radio frequency energy transmitted by the reader into direct current energy; an energy storage module 211, coupled to the energy conversion module 210, for storing the energy converted by the energy conversion module 210.

For example, the energy conversion module 210 may be a rectifier.

For example, the energy storage module 211 may be a capacitor.

The capacitance as a capacitor of the energy storage module 211 may be larger than the on-chip capacitance 204. Alternatively, the capacitance of the energy storage module 211 and the on-chip capacitance 204 may be the same specification.

Therefore, the passive tag 2 is additionally provided with a charging process at the beginning of starting, the newly-added energy collection module 21 is used for fully collecting the radio frequency energy of the reader, and during the subsequent normal starting and working period, the processing module 20 is powered by the energy collection module 21, so that the limitation of the processing module 20 on the working distance is basically eliminated.

Specifically, in the conventional passive tag 1 shown in fig. 1, the load of the rectifier 11 includes all other devices remaining in the passive tag 1. In the passive tag 2 shown in fig. 3, the load of the rectifier serving as the energy conversion module 210 is the capacitor serving as the energy storage module 211, and the load is significantly reduced. The rf power of the reader only needs to support the second demodulator 200 and the energy storage module 211.

It can be seen that, because the power consumption of the energy collection module 21 is significantly less than the power consumption of the processing module 20, according to the energy transmission principle that the distance and the energy are in the inverse square relationship, on the premise that the radio frequency energy of the reader is not changed, because the load is reduced, the energy required for charging the passive tag 2 in this embodiment is reduced, even if the distance from the reader is increased, the passive tag 2 in this embodiment can still effectively complete the charging operation, so that it is possible to extend the working distance.

Further, in the radio frequency same-frequency energy collection tag provided by this embodiment, the power path and the communication link are still the same-frequency and the same-frequency, and the radio frequency energy of the reader is collected in the special energy collection module 21 first, and after the charging is completed, the passive tag 2 of this embodiment starts to perform normal command transceiving operation again. In terms of hardware, the passive tag 2 can be realized only by additionally arranging the energy collecting module 21, and has great advantages in cost, volume and safety. For the reader, additional hardware is not needed, and the implementation is facilitated.

In other words, in the passive tag 2 of the present embodiment, the energy collection module 21 is first charged based on the radio frequency energy of the reader, and then the processing module 20 is powered by the energy collection module 21 during actual operation. Therefore, during the operation of the passive tag 2, the radio frequency energy of the reader basically only needs to satisfy the power consumption of the second demodulator 200 and the energy collection module 21, and the power consumption of the second demodulator 200 and the energy collection module 21 is significantly less than that of other devices in the processing module 20, most of the devices in the processing module 20 do not depend on the real-time energy of the reader any more, the limitation of the processing module 20 on the working distance is eliminated, and the working distance is effectively prolonged.

In one implementation, the energy collection module 21 may further include: a trigger switch 212, said trigger switch 212 being switchable between an open state and a closed state to open or close an electrical connection between said energy storage module 21 and said processing module 20.

In particular, the design of the trigger switch 212 is advantageous to ensure that the processing module 20 is not activated until sufficient energy is collected by the energy collection module 21 to prevent premature consumption of the energy stored on the energy storage module 211.

For example, in a charging phase, the trigger switch 212 is turned off, and the energy conversion module 210 converts the radio frequency energy of the reader received by the receiving antenna 22 into direct current energy and stores the direct current energy into the energy storage module 211. At this point, the open trigger switch 212 ensures that no additional devices in the passive tag 2 consume the rf power of the reader.

For another example, after the charging is completed, the trigger switch 212 is closed, and the energy storage module 211 is electrically connected to the processing module 20 to supply power to the processing module 20.

In one implementation, the supplying power to the processing module 20 during the operation of the processing module 20 includes: when the energy collected by the energy collection module 21 reaches a preset threshold, the energy collection module 21 starts to supply power to the processing module 20.

Specifically, the preset threshold may be determined according to the energy consumed by a single operation of the passive tag 2. For example, the single operation may refer to receiving a sequence containing a command signal once from the reader.

Further, the energy collection module 21 may further include: a Voltage detection module (Voltage Detector)213, coupled to the energy storage module 211, configured to detect whether energy stored in the energy storage module 211 reaches a preset threshold, where the Voltage detection module 213 may also be coupled to the trigger switch 212, and when it is detected that the energy stored in the energy storage module 211 reaches the preset threshold, the trigger switch 212 is controlled to switch to a closed state.

Thus, after the energy collection module 21 collects enough energy, the power-up of the processing module 20 can be controlled to ensure that the energy collection module 21 can support the energy required by the processing module 20 during normal start-up and operation.

In one implementation, the supplying power to the processing module 20 during the operation of the processing module 20 may include: when receiving a trigger command sent by the reader, the energy collection module 21 starts to supply power to the processing module 20.

In particular, the trigger instruction may be used to indicate that the reader is about to start transmitting a command signal.

For example, the trigger command may be a preset number of handshake signals, and the handshake signals may be generated according to a non-standard or customized protocol previously achieved by the reader and the passive tag 2.

Further, the energy collection module 21 may further include: a handshake module 214, configured to receive a trigger instruction sent by the reader, where the handshake module is coupled to the trigger switch 212, and when receiving the trigger instruction, controls the trigger switch 212 to switch to a closed state.

Thus, the improved passive tag 2 provided by the present embodiment can be applied to a scenario where a single reader manages a plurality of passive tags 2. Specifically, the passive tag 2 is controlled to start to operate by a trigger instruction of the reader, so that the passive tag 2 can be effectively prevented from being interfered by signals of other readers. For example, the handshake signals of different readers may be different and unique, and only the passive tag 2 managed by the reader may be identified and respond appropriately by the handshake module 214.

In one implementation, the handshake module 214 may include: a Data-long-0Demodulator (215) for recognizing a handshake signal from the signal transmitted from the reader; a Counter (Counter)216 coupled to the handshake signal processing submodule 215 to count the number of received handshake signals, and determine that the trigger instruction is received when the number of received handshake signals reaches a preset number.

In one implementation, the low level length of the handshake signals may be different from the low level length of the command signals.

For example, referring to fig. 4 and 5, compared to the command signal (data-0) with the high and low levels of 12.5 microseconds (us) commonly used in the prior art, the solution of the present embodiment designs a handshake signal (data-0) with the high level of 12.5us and the low level of 37.5us, so that the handshake signal and the command signal sent by the reader can be distinguished.

Accordingly, the handshake signal processing sub-module 215 identifies the handshake signals from the sequence transmitted from the reader, and counts the number of identified handshake signals by the counter 216, and determines that the trigger instruction is received when a sufficient number of handshake signals are identified.

In one implementation, different readers may design the handshake signals with different low-level lengths to be distinguished from the handshake signals of other readers.

In one implementation, the triggering instructions for different readers may include different numbers of handshaking signals.

In one implementation, the handshake signal processing sub-module may be composed of a common demodulator and subsequent switches, resistors, capacitors, and comparators to identify the handshake signals sent by the corresponding reader.

For example, referring to fig. 6, the handshake signal processing sub-module 215 may include: a first resistor 61, a second resistor 62, a third resistor 63, a fourth resistor 64 and a first switch 65, wherein a first end 61a of the first resistor 61 and a first end 65a of the first switch 65 are connected to the voltage source VDD in parallel, a second end 65b of the first switch 65 is connected to a first end 63a of the third resistor 63 in series, a second end 61b of the first resistor 61 is connected to a first end 62a of the second resistor 62 in series, a second end 63b of the third resistor 63 is connected to a first end 64a of the fourth resistor 64 in series, a second end 62b of the second resistor 62 is grounded, and a second end 64b of the fourth resistor 64 is grounded; the first demodulator 66 is configured to demodulate a signal sent by the reader, where the signal is a handshake signal or a command signal, and the demodulator 66 controls the first switch 65 to be turned on or turned off according to a high-low level of the demodulated signal; a first capacitor 67 connected in parallel with the fourth resistor 64; the comparator 68 is configured to compare a difference between a first voltage V2 and a second voltage V3, where the first voltage V2 is a voltage value of the second end 61B of the first resistor 61, and the second voltage B3 is a voltage value of the first capacitor 67, when the signal sent by the reader is a command signal, the comparator 68 outputs a first comparison result, and when the signal sent by the reader is a handshake signal, the comparator 68 outputs a second comparison result, where the second comparison result is used to indicate that the handshake signal is recognized.

Thus, referring to fig. 7 and 8, by properly designing the values of the first resistor 61, the second resistor 62, the third resistor 63, the fourth resistor 64 and the first capacitor 67, it is possible to: when a standard command signal (Data-0) arrives, the circuit output V4 of the comparator 68 is kept high, which is the first comparison result; when a handshake signal (Data-long-0) arrives, the circuit output V4 of the comparator 68 will output a high/low staggered signal, which triggers the following counter 216 to increment by one.

For example, referring to fig. 6 to 8, when the signal V1 demodulated by the first demodulator 66 is at a high level, the first switch 65 is controlled to be closed, and the second voltage V3 gradually rises to VDD.

When the signal V1 demodulated by the first demodulator 66 is at a low level, the first switch 65 is controlled to be turned on, and the second voltage V3 gradually decreases.

During this time, the first voltage V2 is always VDD/4.

Further, when the command signal is demodulated by the first demodulator 66, the second voltage V3 is always greater than the first voltage V2 because the low level is short. Accordingly, the first comparison result output by the comparator 68 is always high.

Since the low level length of the handshake signal is greater than the low level length of the command signal, the longer low level interval makes it possible for the voltage value of the second voltage V3 to decrease below the first voltage V2 and then return to above the first voltage V2 in the next high level interval. Accordingly, the second comparison result output by the comparator 68 includes high-level and low-level signals, and is a signal in which high-level and low-level are interleaved.

When the first comparison result is received, the counter 216 does not respond any more.

Every time a handshake signal is received as a second comparison result, the counter 216 increments by one, and when the counting result of the counter 216 reaches a preset value, it is determined that the trigger command is received.

In a modification, the first comparison result can be always at a low level by adjusting the input/output manner of the comparator 68.

In a variant, the length of the high level of the handshake signals may be different from the length of the high level of the command signals. Accordingly, by adjusting the control logic of the first demodulator 66 to the first switch 65, the comparator 68 may also be caused to output a first comparison result when the command signal is received, and the comparator 68 may be caused to output a second comparison result when the handshake signal is received.

In a variant, the handshake signal may also be a sequence of other, more complex, tamper-proof signals.

In one implementation, the supplying power to the processing module 20 during the operation of the processing module 20 may include: when the energy collected by the energy collection module 21 reaches a preset threshold and a trigger instruction sent by the reader is received, the energy collection module 21 starts to supply power to the processing module 20.

For example, in addition to the voltage detection module 213 and the handshake module 214, the energy harvesting module 21 may further include: and gate 217, coupled to the voltage detection module 213, the handshake module 214 and the trigger switch 212, wherein when a first message (VCS _ GOOD) received from the voltage detection module 213 indicates that the energy stored in the energy storage module 21 reaches the preset threshold value, and a second message (CNT _ DONE) received from the handshake module 214 indicates that the trigger command is received, the and gate 217 sends a third message (CMD _ COMING) to control the trigger switch 212 to switch to the closed state.

Since the distances from the plurality of passive tags 2 to the reader may be different, the energy storage module 211 of the passive tag 2 farthest from is charged with electricity for a different time period than the energy storage module 211 of the passive tag 2 closest to. By designing a sufficient number of handshake signals, the passive tag 2 is prevented from being activated prematurely, ensuring that the energy storage module 211 has sufficient energy to support completion of the command when the command actually arrives.

Fig. 9 is a flowchart of a method for starting a passive tag according to an embodiment of the present invention. The passive tag in this embodiment may include the passive tag 2 in the technical solutions shown in fig. 3 to fig. 8.

Specifically, the method for starting the passive tag 2 in this embodiment may include the following steps:

step S101, receiving a first sequence;

step S102, performing energy collection operation according to the first sequence;

step S103, after the energy harvesting operation is completed, receiving a second sequence, where the second sequence includes the command signal.

Therefore, by adopting the scheme of this embodiment, the start operation and the charging operation of the passive tag 2 are asynchronously implemented, when the second sequence is received, the energy supporting the operation of the processing module 20 mainly comes from the energy collection module 21 rather than the radio frequency energy of the reader, and since the power consumption of the energy collection module 21 is significantly smaller than the power consumption of the processing module 20, even if the distance between the passive tag 2 and the reader in this embodiment is further increased compared with the limit operating distance of the conventional passive tag 1, which results in a large energy loss when the first sequence and the second sequence reach the passive tag 2 in this embodiment, the passive tag 2 in this embodiment can still effectively charge based on the first sequence, and complete the normal command transceiving operation based on the second sequence, so that the operating distance can be extended.

In one implementation, referring to fig. 10, the first sequence (customized sequence) may include: a charging sequence comprising a plurality of consecutive high levels; an indication sequence is initiated, including at least one handshake signal.

In one implementation, the length of the charging sequence may be determined based on the distance from the reader.

In a specific implementation, before the step S103, the starting method according to this embodiment may further include: receiving a trigger instruction; receiving the second sequence in response to receiving the trigger instruction.

For example, the trigger instruction may be based on a preset number of handshake signal indications.

The second sequence may be equivalent to a normal start sequence of the existing passive tag 1 shown in fig. 2, and in the present embodiment, RF co-frequency energy collection is realized by inserting the specially designed first sequence before the second sequence.

In one implementation, the first sequence may include a Continuous Wave (CW Wave) with a time length of T _ store _ power, that is, the charging sequence. For example, T _ custom _ powerup is 2 seconds(s). Further, the first sequence may further include N handshake signals, i.e., the start indication sequence.

In a typical application scenario, the start-up process of the passive tag 2 may include:

the reader starts to send an R & gtT sequence, the R & gtT sequence comprises a first sequence and a second sequence according to the time sequence, and the first sequence comprises a charging sequence and a starting indication sequence according to the time sequence.

Within the charging sequence, i.e., within a CW wave of length T _ store _ powerup, the energy conversion module 210 charges the energy storage module 211. Accordingly, the voltage VCS of the energy storage module 211 begins to rise.

When the voltage VCS of the energy storage module 211 is charged to the predetermined threshold VH, the voltage detection module 213 generates a VCS _ GOOD signal that enables the handshake signal processing sub-module 215.

In the next start indication sequence, the handshake signal processing sub-module 215 identifies handshake signals (Data-long-0) from the received start indication sequence, and the counter 216 may generate a CNT _ DONE signal after N handshake signals are identified and counted.

In response to receiving the VCS _ GOOD and CNT _ DONE signals, both high, the and gate 217 may generate a CMD _ command signal to indicate whether a command sequence comes after a power up time (T _ powerup). Wherein the CMD _ command signal can be understood as a trigger command.

In response to receiving the CMD _ COMING signal, the trigger switch 212 is closed, and the energy storage module 211 charges the on-chip capacitor 204, entering a normal start-up process.

During the second sequence of power-up times, the voltage VC of the on-chip capacitance 204 gradually increases. Accordingly, the output voltage VDD of LDO202 gradually rises, and when VDD rises to the power-on reset POR threshold, the other block 203 generates a POR pulse. To this end, the BB unit is ready to operate to receive commands.

It can be seen that a certain length of CW wave in the first sequence can be used to accumulate sufficient energy, which is indicated by VCS reaching the target value VH, the achievement of which can be monitored by the voltage detection module 213. While N consecutive handshake signals are used to inform the passive tag 2 that a command is about to start transmitting, a normal start-up procedure can be started.

Without a CW wave of sufficient length and voltage detection module 213, it would not be known whether the energy storage module 211 is sufficiently charged.

Without a trigger command consisting of N consecutive Data-long-0, if the trigger switch 212 is closed and starts the processing module 20 as long as VCS reaches VH, the passive tag 2 may start too early, prematurely consume energy on the energy storage module 211, and may not have enough energy on the energy storage module 211 to support completion of the command when the command really arrives.

Next, the power channel in the forward link when the passive tag 2 of this embodiment is in operation is analyzed.

In a charging phase corresponding to the charging sequence:

when the energy conversion module 210 charges the energy storage module 211, the output voltage of the energy conversion module 210 gradually increases from 0, and when the energy conversion module is charged to the preset threshold VH, the voltage VCS on the energy storage module 211 does not increase any more, and reaches a steady state (steady state).

At this time, the output power Pout _ rect of the energy conversion module 210 is Iout _ rect × VH, PANT × Efficiency _ rect, where Iout _ rect is the output current of the energy conversion module 210, PANT is the received power of the receiving antenna 22 of the passive tag 2, and Efficiency _ rect is the conversion Efficiency of the energy conversion module 210.

Assuming that the impedances of the receiving antenna 22 and the energy conversion module 210 are perfectly matched, the input power PIN of the receiving antenna 22 is PANT. Note that when the highest charging voltage (i.e. the preset threshold VH) is reached, the output current Iout _ rect of the energy conversion module 210 and the current consumption of the circuit hung on the VCS are equal, and here, since the trigger switch 212 is in the on state, the current consumption of the circuit hung on the VCS is the current Ivd of the voltage detection module 213. That is, Iout _ rect is Ivd.

By combining the above two equations, the minimum required received power PANT (min, ss) of the receiving antenna 22 required to satisfy the steady state is VH × Ivd/Efficiency _ rect.

Assuming that VH is 2.15V, Ivd is 0.1uA, and Efficiency _ rect is 20%, the minimum required received power PANT (min, ss) of the receiving antenna 22 can be obtained as 1.075 uW.

After reaching the steady state, the energy conversion module 210 may continuously charge the energy storage module 211, and after the charging is completed, the processing module 20 may start to operate in response to receiving the trigger instruction. This period may be referred to as a Dynamic process.

The dynamic process may include two stages, where the first stage is a charging stage, and refers to charging the electric quantity of the energy storage module 211 to a preset threshold VH within a time length of T _ store _ powerup corresponding to the charging sequence shown in fig. 10; the second phase is the discharging phase, i.e. the processing module 20 starts to operate, consuming the energy stored on the energy storage module 211.

During the charging phase, the main concerns are: how much PANT is needed, the energy storage module 211 may be charged to the preset threshold VH for a given time T _ store _ powerup. Assuming that the Efficiency of the energy conversion module 210 is not changed in the whole charging process, the output power Pout _ rect of the energy conversion module 210 is PANT × Efficiency _ rect.

This output power Pout _ rect is only used to maintain the power consumption (average 0.5VH x Ivd) of the circuits (here, the voltage detection module 213) hanging on the energy storage module 211, since the trigger switch 212 is off and the processing module 20 is not activated.

The energy Est stored in the energy storage module 211 is 0.5 × VH ^2 × CS ═ (Pout _ rect-0.5 × VH × Ivd) × T _ custom _ powerup, where CS is a capacitance value of the energy storage module 211.

During the discharging phase, i.e. during the subsequent operation of the passive tag 2, the processing module 20 is consuming charge, while the energy conversion module 210 is also charging the energy storage module 211.

The single operation time of the processing module 20 is related to a specific command sequence, but the maximum value is constant, and is herein referred to as Ttag _ op. The minimum supply voltage VL of the processing module 20 is determined by the circuit design, for example around 1.6V.

The charge Qout on the energy storage module 211 required for a single operation is equal to Itag _ core × Ttag _ op + Ivd × Ttag _ op. Wherein Itag _ core is the current of the processing module 20, which can be used to measure the chip power consumption (i.e. the power consumption of the processing module 20).

The consumed stored charge Qst ═ CS × (VH-VL), where VH-VL ═ Δ VCS is the energy consumed by a single operation of the passive tag 2.

The charging charge Qin of the energy conversion module 210 is Iout _ rect × Ttag _ op.

Based on charge conservation, there may be Qin + Qst — Qout.

The output current Iout _ rect of the energy conversion module 210 varies with the output voltage of the energy conversion module 210, but because VH and VL are close, Iout _ rect ≈ Ivd, and thus there may be CS × (VH-VL) ≈ Itag _ core × Ttag _ op.

Due to the process withstand voltage limitation, the preset threshold VH generally has a certain upper limit, for example, about 2V, and the minimum value of the capacitance CS of the required energy storage module 211 can be calculated.

Assuming that Itag _ core is 10uA, Ttag _ op is 50ms, VL is 1.65V, and VH is 2.15V, CS is 1 uF.

This may result in the minimum output power of the reader required to meet the dynamic process (i.e., within T _ store _ powerup) to charge the energy storage module 211 to VH:

given VH 2.15V, Ivd 0.1uA, Efficiency _ rect 20%, and T _ custom _ powerup 1s, PANT (min, dyn) 12.09uW (-19dBm) can be obtained.

Obviously, extending T _ custom _ powerup may result in smaller power requirements.

For example, when T _ custom _ powerup is 5s, PANT (min, dyn) is 2.85uW (-25 dBm).

When T _ custom _ powerup is 10s, PANT (min, dyn) is 1.693uW (-27 dBm).

Combining the steady state and dynamic process limitations on the received power PANT of the receive antenna 22, it can be seen that the received power PANT of the receive antenna 22 is generally more limited by the dynamic process: PANT (min) max (PANT (min, ss), PANT (min, dyn)) ═ PANT (min, dyn).

Note that, in the case of a standard passive tag, assuming that the recitifier Efficiency is 40% at this time, the transient received power PANT is 10uA × 1.65/0.4, 41.25uW (-13.84 dBm).

It can be seen that, with the solution of the present embodiment, it is easier to improve the sensitivity of 6dBm, i.e. to extend the distance by more than one time.

Fig. 11 and 12 show the minimum required received power pant (min) of the conventional passive tag and the passive tag 2 according to this embodiment as a function of RF Energy Harvesting (RFEH) time for different chip power consumptions.

Specifically, fig. 11 shows a variation of the minimum required received power pant (min) of the existing passive tag and the passive tag 2 according to the present embodiment with the RF energy collection time when Itag _ core is 10 uA; fig. 12 shows a variation of the minimum required received power pant (min) of the existing passive tag and the passive tag 2 according to the present embodiment with the RF energy collection time when Itag _ core is 2.5 uA.

Wherein the RF energy collection time is a time length T _ custom _ powerup of the charging sequence.

In fig. 11 and 12, the abscissa is both the RF energy collection time (T _ store _ powerup) and is in seconds(s); the ordinate is the minimum required received power pant (min) of the receiving antenna 22 and is in decibel-milliwatts (dBm).

In fig. 11, a curve a1 represents a variation trend of the minimum required received power pant (min) with the RF energy collection time of the conventional passive tag (such as the passive tag 1 shown in fig. 1) when Itag _ core is 10uA, and a curve a2 represents a variation trend of the minimum required received power pant (min) with the RF energy collection time of the passive tag 2 described in this embodiment when Itag _ core is 10 uA.

In fig. 12, a curve a3 represents a variation trend of the minimum required received power pant (min) with the RF energy collection time of the conventional passive tag (such as the passive tag 1 shown in fig. 1) when Itag _ core is 2.5uA, and a curve a4 represents a variation trend of the minimum required received power pant (min) with the RF energy collection time of the passive tag 2 described in this embodiment when Itag _ core is 2.5 uA.

Generally, the chip power consumption Itag _ core is 2.5uA, which represents the highest level of the current industry, and as can be seen from fig. 12, even if the energy collection module 21 of the present embodiment is not added, that is, the radio frequency energy collection technology of the present embodiment is not used, the sensitivity of the conventional passive tag can reach about-20 dBm. If the passive tag 2 according to the present embodiment is used, the sensitivity can be further improved to approximately-30 dBm by the RFEH process.

As can be seen from fig. 11, for the passive tag with Itag _ core of 10uA, the sensitivity is substantially maintained at-13.8 dBm (corresponding to curve a1) as the rf energy harvesting technique described in this embodiment is not employed; as with the RF energy harvesting technique described in this example, a sensitivity of-19 dBm (corresponding to curve a2) was achieved by energy harvesting module 21 harvesting energy over a period of 1 s. The sensitivity can be further improved by prolonging the energy collecting time, and the prolonging ratio of the time and the improving ratio of the sensitivity are not in a linear relation. The appropriate time is 2-6 s, and the sensitivity of-22 dBm to-26 dBm can be achieved.

As can be seen from fig. 12, for the passive tag with Itag _ core of 2.5uA, the sensitivity is substantially maintained at-19.8 dBm (corresponding to curve a3) as the rf energy harvesting technique described in this embodiment is not employed; as with the RF energy harvesting technique described in this example, a sensitivity of-24.6 dBm (corresponding to curve a4) was achieved by energy harvesting module 21 harvesting energy over a period of 1 s. The time of 2-6 s is prolonged, and theoretically, the sensitivity of-27 dBm to-29.9 dBm can be achieved.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A passive tag, comprising:

the processing module is used for receiving a command signal sent by the reader;

the energy collecting module is coupled with the processing module and used for collecting and storing the energy transmitted by the reader and supplying power to the processing module during the operation of the processing module.

2. The passive tag of claim 1, wherein said supplying power to said processing module during operation of said processing module comprises:

when the energy collected by the energy collection module reaches a preset threshold value and/or a trigger instruction sent by the reader is received, the energy collection module starts to supply power to the processing module.

3. The passive tag of claim 2, wherein the predetermined threshold is determined based on the energy consumed by a single operation of the passive tag.

4. The passive tag of claim 1, wherein the energy harvesting module comprises:

the energy conversion module is used for converting the radio frequency energy transmitted by the reader into direct current energy;

the energy storage module is coupled with the energy conversion module and used for storing the energy converted by the energy conversion module;

a trigger switch switchable between an open state and a closed state to break or make an electrical connection between the energy storage module and the processing module.

5. The passive tag of claim 4, wherein the energy harvesting module further comprises:

a voltage detection module coupled to the energy storage module for detecting whether the energy stored by the energy storage module reaches a preset threshold,

the voltage detection module is further coupled with the trigger switch, and when the energy stored in the energy storage module is detected to reach the preset threshold value, the trigger switch is controlled to be switched to a closed state.

6. The passive tag of claim 4, wherein the energy harvesting module further comprises:

a handshake module for receiving the trigger command sent by the reader,

the handshake module is coupled with the trigger switch, and controls the trigger switch to be switched to a closed state when receiving the trigger instruction.

7. The passive tag of claim 4, wherein the energy harvesting module further comprises:

the voltage detection module is coupled with the energy storage module and used for detecting whether the energy stored by the energy storage module reaches a preset threshold value;

the handshake module is used for receiving a trigger instruction sent by the reader;

and the AND gate is coupled with the voltage detection module, the handshake module and the trigger switch, and controls the trigger switch to be switched to a closed state when a first message received from the voltage detection module indicates that the energy stored by the energy storage module reaches the preset threshold value and a second message received from the handshake module indicates that the trigger instruction is received.

8. A passive tag according to claim 6 or 7, wherein the handshake module comprises:

the handshake signal processing submodule is used for identifying handshake signals from the signals sent by the reader;

and the counter is coupled with the handshake signal processing submodule to calculate the number of the received handshake signals, and when the number of the received handshake signals reaches a preset number, the trigger instruction is determined to be received.

9. The passive tag of claim 8, wherein the length of the low level of the handshake signals is different from the length of the low level of the command signals, or wherein the length of the high level of the handshake signals is different from the length of the high level of the command signals.

10. The passive tag of claim 8, wherein the handshake signal processing sub-module comprises:

the voltage regulator comprises a first resistor, a second resistor, a third resistor, a fourth resistor and a first switch, wherein a first end of the first resistor and a first end of the first switch are connected to a voltage source in parallel, a second end of the first switch and a first end of the third resistor are connected in series, a second end of the first resistor and a first end of the second resistor are connected in series, a second end of the third resistor and a first end of the fourth resistor are connected in series, a second end of the second resistor is grounded, and a second end of the fourth resistor is grounded;

the first demodulator is used for demodulating a signal sent by the reader, the signal is a handshake signal or a command signal, and the first demodulator controls the first switch to be opened or closed according to the high-low level of the demodulated signal;

a first capacitor connected in parallel with the fourth resistor;

the comparator is used for comparing the difference between a first voltage and a second voltage, the first voltage is the voltage value of the second end of the first resistor, the second voltage is the voltage value of the first capacitor, when the signal sent by the reader is a command signal, the comparator outputs a first comparison result, when the signal sent by the reader is a handshake signal, the comparator outputs a second comparison result, and the second comparison result is used for indicating and identifying the handshake signal.

11. The passive tag of claim 10, wherein the first switch is controlled to be closed when the signal demodulated by the first demodulator is at a high level, and the first switch is controlled to be open when the signal demodulated by the first demodulator is at a low level.

12. The passive tag of claim 11, wherein the handshake signals have a length of a low level that is greater than a length of a low level of the command signal, wherein the first comparison result comprises only a high level signal or a low level signal, and wherein the second comparison result comprises a high level and a low level signal.

13. A method of activating a passive tag, the passive tag comprising the passive tag of any of claims 1 to 12, the method comprising:

receiving a first sequence;

performing an energy harvesting operation according to the first sequence;

after the energy harvesting operation is completed, receiving a second sequence, the second sequence including the command signal.

14. The method of starting according to claim 13, wherein the first sequence comprises:

a charging sequence comprising a plurality of consecutive high levels;

an indication sequence is initiated, including at least one handshake signal.

15. The activation method of claim 14, wherein the length of the charging sequence is determined based on a distance from the reader.

16. The method of starting according to claim 13, further comprising, after the energy harvesting operation is completed, prior to receiving a second sequence:

receiving a trigger instruction;

receiving the second sequence in response to receiving the trigger instruction.